Thanks a lot for your help so far jfrazierjr. I'm working through the tutorial some more and I'm making some progress. Starting to understand why I'm doing stuff and what each thing does.

I'm stuck again at a pretty silly part though. In the second part of the tutorial, he says create a new layer and fill it with 50% grey. I've searched gimp, I've googled, I'm still not sure how to do it. How do I fill the layer with 50% grey?